Yu Darvish felt a mixture of relief and disappointment when another MRI revealed a stress reaction in his right elbow, a season-ending assessment that confirmed his own suspicions and silenced the doubts about whether or not the Cubs pitcher was really injured.

Alex Rodriguez got it wrong last month when he used his “Sunday Night Baseball” platform to question Darvish’s toughness, second-guess his rehab schedule and hint that it might be dividing the clubhouse. With all his national assignments and off-the-field interests, A-Rod couldn’t possibly see the entire landscape and understand all of the team’s dynamics. But even Darvish admitted that this process dragged on so long that it got into his head.

“Some people referred to this as my weakness on the mental side,” Darvish said Thursday through a translator. “Because there was this uncertainty this whole time, I kind of speculated that the mental side might be a factor. But with the diagnosis, I’m...